Boiler



Aug., l2, 1941. J. P. sEAMoNs lBGILER Filed Aug. 1s, 1940 4 Sheets-Sheet1 J. P. sEAMoNs @252,140

BQILER Filed Aug. 19, '1940 4 Sheets-Sheet .2

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J. P. SEAMONS BOILER Filed Aug. 19, ,-1940 4 kSheets-Sheet 3 Alllllk@www Mug., l@ WM. J. P. sEAMoNs BOILER Filed Aug. 19, l9`40 4Sheets-Sheet 4 Patented Aug. 12, 1941 UNTED STATES TNT FFICE 2 Claims.

This invention relates to steam boilers, and more particularly to smallautomatically controlled boilers for supplying steam to heat the cabinsin airplanes and the like.

An object of the invention is to provide a small, eiiicient boilerconstruction of extremely high capacity for its size and weight.

Another object is to provide a boiler that can be manufactured andmaintained at low cost.

Other more specic objects and features of the invention will appear fromthe detailed description to follow, of a specific embodiment of theinvention as disclosed in the drawings.

Briefly, a boiler in accordance with the invention consists of a watertube boiler of special design for high capacity, efficiency, and economyin construction and maintenance.

As previously indicated, the system is particu-V larly useful as asource of auxiliary heat for aircraft where reliable automatic operationand safety against gasoline leaks are of paramount importance.

In the drawings:

Fig. 1 is a plan view of a twin unit boiler in accordance with theinvention;

Fig. 2 is a front elevation of theV boiler shown in Fig. 1;

Fig. 3 is a vertical sectional view through one of the units of theboiler, the section being taken substantially in the plane III- III ofFig. 1;

Fig. 4 is a plan view with portions broken away of one of the units ofthe boiler, the outer casing shown in Fig. l being removed;

Fig. 5 is a detail elevation view of a portion of the inner unit, theView being taken substantially along the line V-V of Fig. 4;

Fig. 6 is a detail elevational view taken substantially in the planeVI--VI of Fig. 3i;

Fig. 7 is a detail section taken in the plane VII-VII of Fig. 4;

Fig. 8 is a detail section taken in the plane VIII-VIII of Fig. 6;

Fig. 9 is a schematic circuit diagram of a safety control circuit thatmay be employed with the boiler.

As shown in Figs. 1 and 2, the boiler of the present invention consistsof two substantially identical boiler units mounted side by side in acommon outer casing, the construction of each individual boiler unitbeing best shown in Figs. 3, 4, 5, 6, 7 and 8, inclusive. Thus eachboiler comprises an inner shell I and an outer shell 2 interconnected atthe top and bottom and dening an annular water and steam chamber. I'heinner and outer shells I and 2 are spaced relatively close together forabout two-thirds their height but at its upper end the inner shell I isdrawn inwardly to a neck 3, whereas the outer shell 2 is cylindricalthroughout its height. This provides a larger steam and water space atthe upper end than at the lower end. The lower cylindrical portion ofthe inner shell I has a helical ridge or corrugation 4 projectingoutwardly from the main portion of the wall and loosely contacting theouter shell 2. The outer face of the corrugation 4 is preferably weldedto the outer shell 2 at frequent intervals to strengthen the inner shellagainst collapse under high steam pressure. The helical corrugation 4denes a helical path 5 between the inner and outer shells through whichwater tends to circulate downwardly. However, it is desirable, in orderto reduce the frictional resistance to water flow, to provide verticalindentations 6 (Figs. 6 and 8) in the corrugation 4 at frequentintervals to permit direct vertical movement of a portion of the waterso that all oi the water does not have to follow the tortuous helicalpath 5 in order to move from the upper end of the annular chamber to thelower end.

An annular top wall 1 inter-connects the upper edge of the neck 3 andthe outer shell 2, respectively. This end wall 'I also has a pair ofnipples 8 `and 9, respectively, extending therefrom to complete waterand steam connections to the boiler, as will be described later.

The inner shell I defines a flue passage I0 for hot gases from a burnerpositioned immediately below the shell, and this flue is traversed by alarge number of water tubes Il, each of which is connected at its lowerand upper ends to the water and steam space. Thus at its lower end eachof the tubes i I (of which there are four as shown in Fig. 4), is weldedto a nipple or sleeve l2 which extends through the inner shell I and iswelded thereto. Likewise each of these water tubes II is connected atits upper end to a'sleeve I2 which extends through the neck 3.

Each of the sleeves I2 is secured to the inner shell I before itsinsertion into the outer shell 2. This permits welding the sleeve I2 tothe shell I on the outer surface of the latter, which is readilyaccessible prior' to the assembly of the inner and outer shells` Thewater tubes II are assembled within the shell I after the sleeves I2have been welded in place. The use of the sleeves I2 greatly facilitatesthe construction, since it is easier to weld the tubes II to the sleevesI2 than it would be to weld the ends of the tubes I I directly to theshell I. This also facilitates replacement of water tubes, should theybe damaged in service. In operation, the water tubes II become veryhighly heated by the gases moving upwardly through the flue I and thewater within the tubes is rapidly converted into steam. This steamdischarges from the upper ends of the tubes into the relatively largeannular space I4 surrounding the neck 3. At the same time watercirculates by gravity down through the helical passage 5 and through therecesses 6 to the lower end of the boiler, and thence into the lowerends of the tubes I I, where such water is again flashed into steam.

The outer shell 2 of each boiler unit is surrounded by a cylindricalshell I5 which is spaced from the shell 2 to define an annular spacethereabouts. A top closure member I6 is formed with the shell I5. Thegases from-the burner, after passing through the nue I0, circulate downaround the shell 2 in the annular space deiined between the shell 2 andthe shell I5, and escapes through a window I1, near the bottom of thelatter, into a common vent' passage I8 which carries away the productsof' combustion from both boiler units. Thus this passage I8 is'definedin part by the shells I5 of the two boiler unitsl (Figs. 1 and 2) and inpart by rear and front walls I9 and 2U, respectively. A nipple 2| at theupper end of the Walls I9 is provided. to complete connection to a stack22, which can be extended to any desired point of discharge.

The gases from the burner are initially at a very high temperature butlose a great deal of their heat content to the water tubes II duringtheir passage through the iiue I (l. Thereafter, during the passagethrough the annular space between the boiler shell 2 and the surroundingwall I5, they lose further heat to the water circulating through thehelical passage 5. This return flow of the gases down around the outerboiler shell 2 substantially increases the total amount of heattransferred from the gases to the water, and thereby increases theoverall efliciency of the unit.

As previously indicated, the nipples 8 and 9 provide steam connectionsfor purposes to be described later. However, these nipples are not usedto deliver the steamv from the boiler to the discharge line. Insteadsteam is taken from the upper end of the annular chamber I4 through asuperheating tube 25 which passes down through the flue Iil and iscentrally positioned with respect to the water tubes I'I, so thatv it isexposed to the hottest part of the name, to thereby superheat the steamafter its delivery from the space I Il. At its lower end thesuperheating tube 25 passes out through a window 21 in the boiler walls(Figs. l', 2 and 4) The outer ends of the superheating tubes 25 from thetwo boilersare connected by fittings 28 (Figs. 1 and 2) to a commonhorizontal header 29 which in turn connects to a vertical header 30adapted to be connected at its upper endby a fitting 3 Il to a dischargesteam line 32.

The boiler described is primarily intended for operation in a closedsteam heating system, in which the condensate is returned through aseparate line to the boiler. Such a condensate return line is indicatedat 33 in Fig. 2, and is connected to a vertical header 34 which in turnis connected through a check valve 35 to a T-tting 35, the lattercommunicating with a pair of condensate return lines 31 which areconnected by fittings 38 to tubes 39, which extend through the outershell 2 ofthe boiler, as indicated in Fig. 4; so that all condensate isreturned to the lower ends of the helical Water passages in the boilerunit.

The construction of the burner per se is not a part of the presentinvention, and will not be described in detail. The burner units areindicated at "it in Fig. 2 and are supported from the individual boilershells by means of brackets 4I (Fig. 3) formed on the boiler shell andcooperating brackets G2. on the burners. The brackets lil and i2 aredetachably connected together by bolts.

As shown to best advantage in Fig. 3, the boiler shells I and 2 aresecured at their lower edges to an annular frame member 45, the shellsbeing provided with an outwardly extending flange 46 adapted to bebolted to the annular frame 45. The outer casings I5Y are similarlyprovided with outwardly extending flanges l1 adapted to be bolted to theannular frame 45. The latter in turn is supported by suitable standardsi8 which may extend to any supporting base.

If at any time repairs are required on the boiler, the assembly of theshells I and 2 can be removed by first removing the cover casing I5,together with the various gadgets (to be described later) supportedthereon. Thereafter the boiler unit consisting of the shells I and 2 canbe removed from the annular base 45.

The upper end wall 1 (Fig. 4) is preferably provided with radialcorrugations to stiifen it and reduce its tendency to bulge upwardly inresponse to steam pressure.

The construction of the boiler units' proper and the ilues having beenfully described, the control fittings and safety features will now bedescribed with particular reference to Figs. 1 and 2.

Briefly, the boilers are' heated by flames from the burners 45, whichare adapted to use some volatile liquid fuel, such as gasoline. Thisfuel is supplied under pressure from any suitable source through asupply line 55. This supply line 5i) delivers the fuel through anautomatic regulating valve 5I to a line 52. Line 52 delivers the fuelthrough a solenoid valve 53 to a line 54 which connects through aT-fitting 55 with lines 55 going to the two burners 4G.

To enable the boiler to be started from a distance, electrical ignitionis provided; there being a pair of spark plugs 51 mounted on each burnerand connected by high tension leads 58 and insulating bushings 59 to anenergizing line extending through an electrical conduit system SU.

The regulating valve 5I is controlled by the steam pressure in theboilers, and the solenoid valve 53 is under the combined control ofthermostatic means responsive to the flames of the burners i5 and apressure switch S2.

When the solenoid valve is energized, it is in open condition to permitfuel to iiow from line 52 to line 54, but closes whenever the solenoidis dse-energized.

Referring to Fig. 9, the winding 53a of the solenoid valve 53 isconnected in series with the contacts 62a of the pressure switch 62 and*with the contacts 55a of a relay 65, to a source of current (it. Thecontacts 52a are normally closed, but open in response to excess steampressure. The contacts 65a are also normally closed, but open inresponse to energization of relay 65, which is normally de-energizedwhen the boiler is in operation. The operating circuit of relay B5includes the source 66 and the contacts of a pair of sensitive relays 51and 68, respectively. The windings of relays 61 and 68 are connected tothermocouples 69 and 10, respectively, which are positioned immediatelyabove the burners (5U-40, respectively. So long as the burners are inoperation, current is generated in the thermocouples 69 and 'I0 toenergize the relays 6l and 68 and hold their contacts open so that therelay 65 is de-energlzed and its contacts 65a are closed. However,should the name of either of the burners IML-IIJ be extinguished for anyreason, tl'ie associated relay 61 or B is quickly de-energized to closeits contacts and energize the relay 65 which thereupon opens itscontacts 65a to deenergize the winding 53a of the solenoid valve 53, andshut off the fuel supply to the burners.

It will be apparent that winding 53a will also be cle-energized shouldthe steam pressure rise sufficiently to open contacts 52a of thepressure valve 62.

Likewise, should the current supply from the source 66 fail for anyreason, the valve will be closed to shut off the fuel supply.

A manual switch |50 is shunted across the contacts 65a to complete thecircuit to the solenoid winding 56a at the time of starting. This isnecessary because when the thermocouples 69 and 'I0 are cold the relays6l and 68 are deenergized to close their contacts and complete anenergizing circuit to the relay 65 so that its contacts 65a are open.

It will be observed from Fig. 2 that the upper end of the steamconnection |08 on the right boiler unit is connected by a pipe I I5 to aT-connection II6 on the left boiler unit. This is for the purpose ofinterconnecting the upper portions of the two boiler units. The lowerportions of the two boiler units are likewise intercon nected by a pipeII'I. These two cross connections, including the pipe |I5 and the pipeII1, maintain the same water level in both boiler units. These crossconnections also equalize the pressures at the upper and lower ends ofthe two boiler units, and prevent pressure surges through i the watergauge glass. A water gauge |20 is connected between the fitting I I6 anda fitting I2I, which connects the pipe ||1 into the lower part of theleft boiler unit.

It isdesirable, in some instances, to provide forced draft in the unitto insure against a reversal of the draft due to external air currentsor changes in air pressure. To this end, a fan |30 may be positionedwithin the common flue between the two boiler units, this fan beingmounted on the upper end of a vertical shaft which extends down throughthe bottom wall of the flue and into an electric motor ISI positionedtherebelow. This electric motor is preferably energized from the samesource of energy 66 (Fig. 9) as is employed to energize the solenoidvalve winding 53a, so that in ease of failure of the power supplied tothe fan, the flame will be extinguished.

Although for the purpose of explaining the invention a specic embodimentthereof has been described in substantial detail, it is to be understoodthat various changes may be made in the particular construction shownwithout departingfrom the invention, which is to be limited only to theextent set forth in the appended claims.

I claim:

1. A boiler of the type described, comprising: a vertical, tubular innerboiler wall defining a passage for heating gases, a tubular outer boilerwall surrounding said inner wall and connected thereto at the top andbottom whereby the two walls together define an annular water chamber, awater tube positioned within said passage and connected at its oppositeends/ to the lower and upper ends, respectively, of said annular waterchamber, said inner wall having a flat-topped helical corrugationextending outwardly therefrom into contact with said outer wall, andwelded thereto at intervals to prevent collapse of said inner wall understeam pressure, said corrugations having vertical grooves extendingtherethrough at intervals tof provide vertical paths for watercirculation.

2. A boiler of the type described, comprising: a vertical, tubular innerboiler wall defining a passage for heating gases, a tubular outer boilerwall surrounding said inner wall and connected thereto at the top andbottom whereby the two walls together deiine an annular water chamber, awater tube positioned within said passage and connected at its oppositeends to the lower and upper ends, respectively, of said annular waterchamber, said inner wall having a helical corrugation extendingoutwardly therefrom into contact with said outer wall, and weldedthereto at intervals to prevent collapse of said inner wall under steampressure, said corrugations having vertical grooves extending therefromat intervals to provide vertical paths for water circulation.

JOSEPH P. SEAMONS.

